This invention relates to a fluid displacement apparatus, and more particularly, to an adjusting mechanism of the angular relationship between spiral elements for a scroll-type fluid displacement apparatus.
Scroll-type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801,182 (Creux) discloses a device including two scroll members each having a circular end plate and a spiroidal or involute spiral element. These scroll members are maintained angularly and radially offset so that both spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scroll members shifts the line contacts along the spiral curved surfaces and, therefore, the fluid pockets change in volume. Since the volume of the fluid pockets increases or decreases dependent on the direction of the orbiting motion, the scroll-type fluid displacement apparatus is applicable to compress, expand or pump fluids.
In comparison with conventional compressors of the piston type, the scroll-type compressor has certain advantages, such as fewer parts and continuous compression of fluid. However, in scroll-type compressors, adjusting the angular relationship between the spiral elements is difficult. If the angular relationship between the spiral elements is in error, the radial sealing points between the two spiral elements are not fully sealed, thus allowing fluid leakage. As a result of the fluid leakage, the efficiency of the compressor is reduced. One solution to the above problem is to reduce the dimensional tolerances of parts. However, manufacturing of the parts is complicated and expensive. Another solution is to limit the offset to maintain the desired angular relationship between the spiral elements. However, since there are many factors other than the offset which may cause the unsuitable angular relationship, this is not a complete solution.
During the assembly of a scroll-type compressor having a ball coupling mechanism, relative angular offset between both scroll members may occur as a result of the following factors;
(1) the relative angular offset between the fixed scroll element and housing;
(2) the relative angular offset between the housing and the front end plate;
(3) the relative angular offset between the front end plate and the fixed ring of the ball coupling mechanism;
(4) the relative angular offset caused by the difference between the inner diameter of the hole formed in the fixed ring of the ball coupling mechanism and the outer diameter of the ball;
(5) the relative angular offset caused by the difference between the outer diameter of the ball and the inner diameter of the hole formed in the movable ring of the ball coupling mechanism; and
(6) the relative angular offset between the movable ring of the ball coupling mechanism and the orbiting scroll member.
In order to compensate for these factors, one technique is to adjust the angular relationship between a first hole formed on the end wall surface of the spiral element of one scroll member and a second hole formed through the front end plate opposite the first hole of the scroll member. Adjusting the angular relationship between both scroll elements is generally accomplished by an angle adjusting member inserted in both holes from outside of the front end plate. However, this technique can compensate only for the relative angular offset in factors (1)-(3) above. The relative angular offset caused by factors (4)-(6) cannot be eliminated using this technique.